Test-Retest Reliability of Diffusion Measures Extracted Along White Matter Language Fiber Bundles Using HARDI-Based Tractography.

Mariem Boukadi,Karine Marcotte,Simona M Brambati,Arnaud Boré,Marianne Chapleau,Maxime Descoteaux,Samuel Deslauriers-Gauthier,Alex Desautels,Christophe Bedetti,Jean-Christophe Houde

doi:10.3389/fnins.2018.01055

Abstract

High angular resolution diffusion imaging (HARDI)-based tractography has been increasingly used in longitudinal studies on white matter macro- and micro-structural changes in the language network during language acquisition and in language impairments. However, test-retest reliability measurements are essential to ascertain that the longitudinal variations observed are not related to data processing. The aims of this study were to determine the reproducibility of the reconstruction of major white matter fiber bundles of the language network using anatomically constrained probabilistic tractography with constrained spherical deconvolution based on HARDI data, as well as to assess the test-retest reliability of diffusion measures extracted along them. Eighteen right-handed participants were scanned twice, one week apart. The arcuate, inferior longitudinal, inferior fronto-occipital, and uncinate fasciculi were reconstructed in the left and right hemispheres and the following diffusion measures were extracted along each tract: fractional anisotropy, mean, axial, and radial diffusivity, number of fiber orientations, mean length of streamlines, and volume. All fiber bundles showed good morphological overlap between the two scanning timepoints and the test-retest reliability of all diffusion measures in most fiber bundles was good to excellent. We thus propose a fairly simple, but robust, HARDI-based tractography pipeline reliable for the longitudinal study of white matter language fiber bundles, which increases its potential applicability to research on the neurobiological mechanisms supporting language.

Highlights

The characterization of the brain and language network and its development, disruption, and changes over time represents one of the central themes of cognitive neuroscience
fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), radial diffusivity (RD), and mean length of streamlines (MLS) measures showed consistently good to excellent test-retest reliability (ICCs = 0.62−0.95) across all four white matter (WM) fiber bundles, bilaterally
AF, arcuate fasciculus; ILF, inferior longitudinal fasciculus; IFOF, inferior fronto-occipital fasciculus; UF, uncinate fasciculus; FA, fractional anisotropy; AD, axial diffusivity; MD, medial diffusivity; RD, radial diffusivity; NuFO, number of fiber orientations; MLS, mean length of streamlines; wDSC, weighted dice similarity coefficient; intra-class correlation coefficient (ICC), Intra-class correlation coefficient estimates; CI, 95% confidence intervals of the ICC. ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001

Summary

Introduction

The characterization of the brain and language network and its development, disruption, and changes over time represents one of the central themes of cognitive neuroscience. While test-retest reliability has already been reported for other neuroimaging techniques that are usually employed in evaluating longitudinal changes in the language brain network (such as resting state and task-based functional MRI, voxel-based morphometry, and cortical thickness; e.g., Jovicich et al, 2009; Zhang et al, 2011; Braun et al, 2012; Birn et al, 2013; Powers et al, 2013; Lin et al, 2015; Seiger et al, 2015; Wang et al, 2016; Madan and Kensinger, 2017; Zhang et al, 2017), test-retest reliability of dMRI-based tractography has received comparatively less attention. While the role of this bundle in language is still controversial, it has been suggested to support semantic retrieval (Lu et al, 2002; Grossman et al, 2004; Catani and Mesulam, 2008) and simple syntactic operations (e.g., processing of phrases) (Friederici et al, 2006)

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